The invention relates to the field of vascular catheters. More particularly, the invention is related to a dilation balloon catheter for use and percutaneous transluminal coronary angioplasty ("PTCA").
PTCA is an efficient and effective method for treating stenoses in coronary arteries. In a typical PTCA procedure, a guide catheter having a pre-shaped distal end is introduced into the patient's cardiovascular system through a femoral or brachial artery. Prior to introducing the guide catheter into the patient, a wire is inserted into the guide catheter to straighten the curved distal end of the catheter. Using fluoroscopy, the surgeon advances the guide catheter into the patient's aorta until the catheter's tip is adjacent to a desired branch artery. The wire is then withdrawn and the tip of the guide catheter engages the ostium of the desired branch artery. A dilation balloon catheter is passed through the guide catheter and into the branch artery. The balloon catheter is maneuvered to place the balloon within the stenosis to be treated. The balloon is inflated and deflated one or more times to compact the stenosis, then removed from the patient. Compacting the stenosis increases the diameter of the passage through the stenosis, thereby increasing the blood flow in the artery.
The most frequently used balloon catheter is the over-the-wire type. An over-the-wire catheter includes a guidewire lumen which extends from the proximal end of the catheter to the distal end. In use, a guidewire is slidably disposed in the guidewire lumen, and the catheter is inserted into and advanced to the distal end of the guide catheter. The guidewire is maneuvered along the patient's artery in order to pass the distal end of the guidewire through the stenosis to be treated. Finally, the catheter is advanced to place the balloon within the stenosis.
Over-the-wire balloon catheters have several inherent advantages. Over-the-wire catheters are quite "pushable," a characteristic which enables the surgeon to apply the force necessary to push the balloon though a tight stenosis. Also, it is possible to leave a guidewire in place within a stenosis while exchanging one over-the-wire catheter for another. Leaving a guidewire in place when exchanging catheters eliminates the need to again maneuver a guidewire's distal end through the stenosis, thereby saving time and decreasing the possibility of causing trauma to the patient. However, since the guidewire is contained within the catheter, for such an exchange to be accomplished, the guidewire's length must be increased to at least twice the length of the catheter. In one known procedure, an extension is added to the proximal end of the original guidewire to achieve adequate guidewire length. In another known procedure, the original catheter is left in place within the stenosis, or advanced as close as possible to the stenosis, and the original guidewire removed and replaced with an "exchange" guidewire of adequate length. Unfortunately, both of these procedures are cumbersome and require two operators to perform.
In some cases, a surgeon may find it is necessary to apply another device (such as a directional atherectomy device, a rotoblation device, or a stent) to a stenosis after using a balloon catheter. Since each of these devices requires a different type of guidewire, another advantage of an over-the-wire catheter is that the surgeon can remove the catheter's guidewire and replace it with another device's guidewire. Using one of the procedures described above, the surgeon can then remove the balloon catheter and replace it with the device. Again, exchanging guidewires eliminates the need to maneuver the device's guidewire to the stenosis to be treated. However, since one of the procedures for providing adequate guidewire length must be performed, replacing a balloon catheter with a device requires two operators.
Another conventional dilation balloon catheter is the fixed-wire type. The fixed-wire balloon catheter includes a short guidewire attached to and extending from the distal tip of the catheter. A fixed-wire catheter is inherently quite steerable, and hence relatively easy to maneuver to the stenosis to be treated. However, fixed-wire balloon catheters are not as pushable as the over-the-wire type. In addition, if it is necessary to change catheters, the new catheter must again be maneuvered to the stenosis to be treated, which requires additional time and increases the risk of trauma.
Rapid exchange catheters, such as that disclosed in U.S. Pat. No. 5,346,505 (Leopold), can be exchanged while leaving the guidewire in place in the patient without using an exchange wire or an extension wire. However, since the guidewire lumen of the catheter extends only a short distance proximally from the distal end of the catheter, the catheter cannot be used to position another guidewire across to the stenosis to be treated. Thus, while one rapid exchange catheter can easily be easily exchanged for another, changing from a rapid exchange catheter to another device requires removal of both the catheter and its guidewire before insertion of the device's guidewire.